1. Field of the Invention
The present invention relates to an apparatus and a method for drying semiconductor wafers and LCD glass substrates, for example, after they are washed by washing solution.
2. Description of the Related Art
In the course of manufacturing semiconductor devices, the semiconductor wafers are washed while immersing them successively in chemical solutions in chemical solution vessels. That solution which adheres to them when they are washed is then removed from them by the substrates-drying apparatus in a drying chamber.
U.S. patent application Ser. No. 08/111,006 discloses a substrates-drying apparatus of this kind. In this substrates-drying apparatus, a volatile process solution such as IPA (isopropylalcohol) is stored in a process solution vessel and it is heated by a heater to generate IPA vapor in the vessel. When the wafers are set above this vapor generating region in the vessel, IPA vapor condenses on them and water which has adhered to them when they are washed is thus removed from them . They can be thus made dry.
In the substrates-drying apparatus of this kind, however, water mixes in IPA in the process solution vessel to thereby lower the substrates-drying capacity of IPA. Therefore, IPA must be replaced by new one when the substrates-drying process is repeated certain times (or every 10-batch).
IPA has a low boiling point (of 60.degree.-80.degree. C.) and it is likely to be inflamed. For safety, therefore, it must be drained from the process solution vessel after its temperature becomes lower than its boiling point.
In the conventional substrates-drying apparatus, however, the heater has a large heat capacity. This prevents IPA from being cooled lower than the boiling point for a shot time. In addition, it takes a long time to replace IPA in the vessel with new one. The substrates-drying capacity is thus made low together with the throughput.